In recent years, a material having a self-healing capability to spontaneously repair the damage generated during use is being developed. Such a material exhibits a remarkably high mechanical reliability and a long use-life, and therefore, is promising as next-generation structural and mechanical materials.
The self-healing function is a phenomenon caused by a chemical reaction, and the self-healing material is in the form of a composite material where a reactant for achieving healing by a chemical reaction (hereinafter, sometimes referred to as “healing-developing material”) is encapsulated in a matrix.
Specifically, a self-healing ceramic material utilizing high-temperature oxidation of a healing-developing material has been proposed (PTLs 1 to 3). In particular, as such a self-healing ceramic material, there has been proposed a particle-dispersed self-healing ceramic material where particles of an oxidizable healing-developing material such as silicon carbide are dispersed and compounded in a ceramic matrix. The healing-developing material is oxidized and expands to fill the crack, and thereby achieves self-healing, when cracking occurs in the ceramic matrix (PTL 3).
This self-healing ceramic material can overcome a major problem of the ceramic material, i.e. a problem of being low in the toughness, and thus susceptible to cracking, despite high heat resistance. For this reason, it is considered to use the self-healing ceramic material in the application requiring both heat resistance and mechanical strength, for example, applications such as gas turbine member, jet engine member, automotive engine member and ceramic spring member (PTL 1).
Incidentally, in an internal combustion engine such as automotive engine, a ceramic component is used in various parts, and many ceramic components are used not only for an engine member requiring both heat resistance and mechanical strength as described above, but also for an exhaust flow path from the internal combustion engine.